1. Field of Invention
The present invention relates to a 3D (three dimension) color information acquisition method and a 3D color information acquisition apparatus for use in 3D model imaging with high resolution. More particularly, the present invention relates to a 3D color information acquisition method and apparatus using more than 3 of major colors to encode a pattern and increase image resolution with a considerable reliability.
2. Related Art
Many 3D image acquisition methods have been provided in the prior art. One approach uses laser to scan topography of an object placed inside a box and to acquire colors of the object. Such a method requires expensive equipment and is time-consuming, which is not very practical in use. Another approach is to project a pattern in the form of color bands or color blocks on an object. A location of every color band or block is determined and compared to that of a reference pattern. Depth data of the object are calculated by using triangle distance measurement.
The profile, texture and material greatly affect the data acquisition for the object. Usually, the number of major constituting colors is 3 or 4 in view of stability. If the number of major constituting colors is higher than 4, then it is difficult to recognize the colors of the object when the pattern is projected on the object. If the number of major constituting colors is lower than 3, then this type of method is not suitable for use in encoding a large-size and high-density object image. It is an important issue to balance the resolution and the stability.
WO 00/70303 uses three basic colors, i.e., Red, Green, and Blue for color encoding. US 2002/0075456 uses four basic colors for color encoding. When the number of basic constituting colors is small, the total number of encoded color bands is small. In WO 00/70303, the number of encoded color bands is less than 100, while in US 2002/0075456 it is less than 64, which are not enough for the requirement of resolution in the current color image field. WO 00/70303 further teaches forming a redundant pattern at a center of the pattern to increase the number of encoded color bands, with a black region between two adjacent color bands. U.S. Pat. No. 6,549,288 uses gradual variation in intensity of light to form structured light pattern. However, the redundant pattern may disappear due to unknown reasons, which causes encoding failure. Furthermore, the color bands are greatly influenced by the object conditions. Reducing color gradation may constitute a solution to satisfy the resolution requirement, but it only partially solves the problem.